SFTP Filezilla Access issue

[searching4answers]

Hi all,
First post here, but I'm desperate. I have a user that tries to establish a connection to an SFTP server using FileZilla. The login information is the same for all of the user's colleagues. All of them establish a connection under the same conditions in the same company environment.
However when this particular users tries to connect they get an error that additional authentication is required and the connection is terminated.
The user has the necessary permissions for port 22.
The user, however, doesn't enter any port when establishing the connection. He explained that no port was required for the connection.
Entering a port results in a different error: server connection attem

The following troubleshooting was performed:
-> Tried connection without VPN
-> Tried connection without Firewall
-> FileZilla reinstalled multiple times (different releases tried: ver. 3.30 and ver 3.65)

Does anyone have any idea?

[botg]

However when this particular users tries to connect they get an error that additional authentication is required and the connection is terminated.

Select the Interactive login type in the Site Manager to see all authentication prompts.